PON is an emerging last-mile optical broadband access technology, where no node device is needed at optical branching points while a simple optical branching device will serve the purpose. Therefore, PON saves fiber resources and equipment room investment, shares bandwidth resources, and has the features of high device security, fast construction, and low comprehensive construction cost.
The PON technology is applicable to an Optical Access Network (OAN). A reference architecture of the OAN is shown in FIG. 1. The OAN consists of a Customer Premises Network (CPN), an Access Network and a Service Node Function (SNF). The CPN has a User Network Interface (UNI) with the access network and T is a reference point of the UNI. The access network has a Service Node Interface (SNI) with the SNF and V is a reference point of the SNI. The CPN mainly includes a Customer Premises Equipment (CPE). The access network includes an Adaptation Function (AF), an Optical Network Unit (ONU)/Optical Network Terminal (ONT), an Optical Distribution Network (ODN), and an Optical Line Terminal (OLT). It should be noted that the PON includes the ONU/ONT and the OLT and the ONU/ONT is connected to the OLT via the ODN.
In the access network, the AF is optional, and provides conversion between the ONU/ONT interface and the UNI. The AF may be built in the ONU, in which case, reference point (a) is unnecessary. The AF may also be placed behind the OLT to provide conversion between the OLT interface and the SNI. The AF may be regarded as either a function of the CPN or a function of the access network. The ONT provides a network interface for the ODN and connects one or more ODNs. The ODN provides transport for the OLT and the ONU. The ONU provides a user side interface for the access network and is connected to the ODN.
For packets sent by the CPE, after the AF receives the packets, the AF may convert the packet format from the UNI format to the format of an interface, such as an Ethernet link, that can be connected to the ONU. Then the ONU converts the packets into a format that can support packet transfer over the ODN, such as the encapsulation format of an Ethernet Passive Optical Network (EPON) and the general frame encapsulation format of a Gigabit Passive Optical Network (GPON). Finally, the OLT converts the packets into a format of an SNI, such as an Ethernet link, and delivers the packets to the SNF. For packets sent by the SNF, a reverse process is followed.
At present, when PON provides backhaul transport for a Base Station (BS), a mobile terminal does not send Ethernet frames but IP packets to the BS and does not use a Media Access Control (MAC) address or a VLAN ID to carry user information. A PON chip in the prior art supports only Ethernet over GPON Encapsulation Method (ETH over GEM) or only Time Division Multiplexing (TDM) packets while bearing of IP packets is not supported.